Automatic blood coagulation analysis devices which automatically measure blood coagulation reaction sample a specimen and reagent by means of a probe from containers holding the specimen and reagent, dispense these into empty cuvettes, place those cuvettes into predetermined measurement ports and execute optical measurement (see Patent Literature 1). One of the measurement parameters of such automatic blood coagulation analysis devices is the measurement of fibrinogen concentration (hereinafter, Fbg concentration) in the specimen.
Measurement of Fbg concentration is performed by adding a thromboplastin reagent (containing tissue thromboplastin and calcium; hereinafter, PT reagent) to the specimen, irradiating the reaction solution with light, and measuring scattered light. When PT reagent is added to the specimen, as the final reaction, the fibrinogen within the specimen changes to fibrin. Fibrinogen is soluble in water, and hardly scatters any light when irradiated with light, while fibrin is insoluble in water and produces scattering when irradiated with light. The intensity of scattered light from the reaction solution to which PT reagent has been added is proportional to the amount of fibrin in the reaction solution, and the amount of fibrin in the reaction solution depends on the amount of fibrinogen in the specimen, so the Fbg concentration in the specimen can be determined by measuring final scattered light intensity from the reaction solution to which PT reagent has been added.